The invention relates to biological treatment of wastewaters using a combination (a true hybrid system) of the activated sludge and the rotating disc filter process (fixed film process). In special the subject of the invention is the simultaneous and integrated nitrification and denitrification as well as the advanced biological P-elimination (luxury-P-uptake).
The elimination of the N- and P-components in a wastewater treatment plant mostly occurs by using biological processes for the elimination of the nitrogen-components (nitrification/denitrification). In most cases phosphates are reduced by chemical processes (chemical precipitation, coagulation and floculation using chemicals with ferrous, alum or calcium compounds). Biological methods for the P-elimination were developed in the last years. They base on an increased incorporation of phosphates into the cells of the microorganisms of the activated sludge, which is higher than usual by an activated sludge microorganism. (see: ATV (1989): Biologische Phosphorentfernung, Journal "Korrespondenz Abwasser" 36, pp 337-348 and Kunst,S, "Untersuchungen zur biologischen Phosphorelimination im Hinblick auf ihre abwassertechnische Nutzung", Institute for water pollution degredation of the University of the city Hannover, publication number 77 (1990).
All techniques for the elimination of the N- and P-compounds are called "advanced wastewater treatment" or "third-stage-treatment".
Fixed film reactors, which are preadded ore joined after an activated sludge biotank, are known from the papers DE-A 29 14 689 or DE-A 31 40 372. To the fixed film reactors--as already mentioned--the so-called RBC-systems (Rotating Biological Contactors or rotating disc filters) as well as the aircatching rotating biological contact aerators will belong, which rotate around a horizontal central shaft and which consists in their cells of a series of plates attached in a defined space, for example made of plastic or similar materials. Construction and operation of the contact aerators are described among other things in the above mentionend papers.
An aircatching rotating biological contact aerator, rotating around a horizontal central shaft (cell segment contact aerator) can be used on the one hand in the function of a trickling filter used in the wastewater treatment technique as a fixed film reactor. So nitrifying bacteriums for the oxidation of the nitrogen compounds can grow in the fixed film so that nitrification is guaranteed.
On the other hand it is possible to adjust the desired mixing of the biotank by using the contact aerators so that a separate mixing and stirring equipment is not necessary.
Actual informations says that it was not yet succesful to integrate an advanced biological P-elimination process into a nitrification/denitrification-system in such a way, that only one tank will be necessary, so that the advanced biological P-elimination in combination with nitrification and denitrification will work simultaneously integrated in the same tank volume.